// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// File provides basic classes and functions for rANS bit encoding.
#ifndef DRACO_CORE_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_
#define DRACO_CORE_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_

#include <vector>

#include "draco/core/ans.h"
#include "draco/core/encoder_buffer.h"

namespace draco {

// Class for adaptive encoding a sequence of bits using rANS.
class AdaptiveRAnsBitEncoder {
  public:
    AdaptiveRAnsBitEncoder();
    ~AdaptiveRAnsBitEncoder();

    // Must be called before any Encode* function is called.
    void StartEncoding();

    // Encode one bit. If |bit| is true encode a 1, otherwise encode a 0.
    void EncodeBit(bool bit) {
        bits_.push_back(bit);
    }

    // Encode |nbits| of |value|, starting from the least significant bit.
    // |nbits| must be > 0 and <= 32.
    void EncodeLeastSignificantBits32(int nbits, uint32_t value) {
        DRACO_DCHECK_EQ(true, nbits <= 32);
        DRACO_DCHECK_EQ(true, nbits > 0);
        uint32_t selector = (1 << (nbits - 1));
        while (selector) {
            EncodeBit(value & selector);
            selector = selector >> 1;
        }
    }

    // Ends the bit encoding and stores the result into the target_buffer.
    void EndEncoding(EncoderBuffer *target_buffer);

  private:
    void Clear();

    std::vector<bool> bits_;
};

}  // namespace draco

#endif  // DRACO_CORE_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_
